EZSA LAK-9

LAK-9 Lietuva
LAK-9M in Monino
Type:	Glider
Design country:	Soviet Union
Manufacturer:	EZSA
First flight:	December 12, 1972 (BK-7A)

The EZSA LAK 9 Lietuva ( Lithuanian Lithuania , Russian ЭЗСА ЛАК-9 Летува ) is the first in GRP construction mass-produced Glider of the Soviet Union . It was developed for the open class . The abbreviation LAK stands for Litowskaja Awiazionnaja Konstrukzija (Литовская Авиационная Конструкция), Lithuanian aircraft construction.

development

The 1968 world glider championships held in Leszno , Poland, made it clear that the traditional wooden aircraft were no longer able to keep up with the world's best, which was increasingly dominated by structures made of glass fiber reinforced plastic or polyester resin. As a result, in 1969 in Prienai, Lithuania, a group of six formed under the leadership of Balys Karvelis on their own initiative to develop a model for this interpretation. At that time, the members had no experience of using epoxy resin and fiberglass in aircraft construction. The optimal manufacturing techniques first had to be determined through tests and since there was no government support, the construction of the prototype known as BK-7A (for Balys Karvelis) with a span of 17 m dragged on until the end of 1972. Since no landing flaps were provided, the landing should take place with the flaps extended to 70 ° . On December 12th, the glider pilot and head of the Kaunas Aviation Club, Aleksandras Jonusas, was finally able to carry out the first flight. Further testing proved so successful that financial resources were approved for the further work of the construction group, which has now grown to twelve people. On this basis, it was possible to build a second BK-7A with airbrakes and a span of 20 m, with which the strength tests that had not been carried out until then were made up for. A third BK-7A was built for further testing.

Another test model was designated as the BK-7B . It was equipped with two 80-liter water ballast tanks and had a weight of 470 kg. The BK-7B was tested with good results from August to September 1975 in Kishinev during the training of the Soviet national team under competitive conditions. Following then the serial production it was decided that in 1969 built in Prienai EZSA ( Russian ЭЗСА, Экспериментальный завод спортивной авиации , Eksperimentalny zavod sportiwnoi awiazi or sport aircraft experimental work) of DOSAAF should be.

The first series version, known as the BK-7C , differed only slightly from the original BK-7B in that ballast tanks were enlarged to 90 liters and there were minor structural changes. The second series was officially named LAK-9 and had a (reduced) set-up mass of 380 kg, adapted to international standards. The 3rd series received ailerons coupled with the flaps . With the first aircraft of this lot, a LAK-9 took part in an international competition, the 1976 World Cup in Räyskälä , Finland . She was flown by Oleg Pasetschnik, but retired early due to severe damage during an outlanding. In the seventh aircraft of the 3rd series, the volume of the water tank was doubled to 180 liters, which resulted in an increase in the wing loading from 38.7 kg / m² to 44.7 kg / m², which should bring about an optimal adaptation to ideal thermal conditions.

The 4th series was implemented at the turn of the year 1976/77 under the name LAK-7M (for modernisirowany, modernized). It can be recognized by the modified canopy and the redesigned cockpit. In addition, flaps and ailerons were installed so that they overlap, which reduced the circle change time from 45 ° to 45 ° in contrast to earlier versions from 7.5 s to 4.5 s.

The LAK-12 appeared as the successor model in 1980 .

construction

The LAK-9 is a self-supporting shoulder wing made of glass fiber reinforced epoxy resin. The two-part wing in a double trapezoidal shape consists of the main spar and ribless half-shells with a slight V-shape. In the wing roots there are two ballast containers that are filled through a central tank nozzle in the landing gear shaft. The tail unit consists of the semi-raised pendulum elevator with spring trim and the rudder with 40 ° deflection. The chassis consists of the sprung, brakable main wheel.

Technical specifications

Parameter	Dates (3rd and 4th series)
crew	1
span	20.02 m
length	7.27 m
height	1.53 m
Wing area	14.99 m²
Wing extension	26.8
Empty mass	382 kg
Payload	maximum 108 kg
Water ballast	180 kg
Takeoff mass	maximum 670 kg
Wing loading	without ballast 32.7 kg / m² maximum 44.7 kg / m²
Best glide ratio	48 at 103 km / h
Slightest sinking	0.51 m / s at 74 km / h
Sliding speed	maximum 210 km / h
Minimum speed	64 km / h
Towing speed	maximum 140 km / h in aircraft tow
g -limit	+6 / −3
profile	Wortmann FX 67 K 170

literature

• Gerold Weber: Flown and approved: "Lietuva" LAK-9, USSR . In: Fliegerrevue . No. 1/1978 , p. 26th ff .

Web links

Commons : LAK-9  - collection of pictures, videos and audio files

• Планер "Летува" ЛАК-9. Retrieved August 17, 2017 (Russian, history, dates, photos).